Browsing by Publisher "Wiley-VCH Verlag"
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Item Cyclopentadienylmolybdenum(VI) and molybdenum(V) oxo chemistry: New synthetic and structural features(Wiley-VCH Verlag, 2002) Saurenz D.; Demirhan F.; Richard P.; Poli R.; Sitzmann H.Convenient syntheses for Cp, Cp*, and related cyclopentadienyl derivatives (4Cp = C5HiPr4i CP‴ = C5H2tBU3-1,2,4) of formula [(Ring)2Mo2O5] are described. Compound [Cp2Mo2O5] was produced in good yields by the rapid oxidation of red [CpMoO2]4 with PhIO in CH2Cl2. [Cp*2Mo2O5] was obtained by CH3COOH acidification of aqueous solutions of [Cp*MoO3]-Na+, the latter being generated in a single step from [Cp*MoCl4] and more than 5 equiv. of aqueous NaOH in air. Minor quantities of [Cp*MoO2]2 were also isolated from this reaction, although the formation of this by-product may be reduced by using a two-step basic hydrolysis procedure. Extension of the latter strategy also allowed the preparation of [4Cp2Mo2O5], [Cp‴2Mo2O5], and [4CpMoO2Cl] in good yields, in addition to the by-product [Cp‴MoO2]2. X-ray structures are reported for compounds [4Cp2Mo2O5], [Cp‴2Mo2O5], [Cp*MoO2]2, [Cp‴MoO2]2, and [4CpMoO2Cl]. © Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.Item Reduction of [Cp*2Mo2O5] in aqueous medium: Structure and properties of a triangular mixed oxo-hydroxo-bridged product, [Cp*3Mo3(μ-O)2(μ-OH) 4](X)2 (X = CF3CO2 or CF 3SO3)(Wiley-VCH Verlag, 2006) Demirhan F.; Çaǧatay B.; Demir D.; Baya M.; Daran J.-C.; Poli R.The reduction of [Cp*2Mo2O5] with Zn in a MeOH/H2O solution acidified with either CF3COOH or CF3SO3H leads to the formation of the [Cp* 3Mo3(μ-O)2(μ-OH)4] 2+ ion as its trifluoroacetate or trifluoromethanesulfonate salt. The structure of the compound was confirmed by X-ray analyses. The anions establish hydrogen-bonding interactions with all four bridging OH groups. Density functional calculations afford bonding parameters in close agreement with the observed structure and indicate that the cluster is best described as a valence-delocalized Mo313+ species. The five metal electrons are distributed among an α-type (z2) orbital, which accounts for most of the metal-metal attraction, and two essentially metal-metal nonbonding e-type (xy) orbitals with a slight Mo(μ-O) π*-type contribution. Because of the C2 symmetry, the latter orbitals are not degenerate. The calculations show that the unpaired electron is located in a molecular orbital with equal contribution from two Mo atoms, in agreement with the experimental observation of coupling of the unpaired electron to two Mo atoms in the isotropic EPR spectrum. © Wiley-VCH Verlag GmbH & Co. KGaA, 2006.Item Aqueous reduction of [Cp*2W2O5]: Characterization of the triangular clusters [Cp*3W 3O4(OH)2]2+ and [Cp* 3W3O6]+ - Comparison with molybdenum(Wiley-VCH Verlag, 2007) Dinoi C.; Sözen P.; Taban G.; Demir D.; Demirhan F.; Prikhodchenko P.; Gun J.; Lev O.; Daran J.-C.; Poli R.Zinc reduction of Cp*2W2O5 in an acidified water-methanol medium affords the green 3-electron trinuclear cluster [Cp*3W3O4(OH)2]2+, isolated and crystallographically characterized as the triflate salt, 1. Upon exposure to air, this complex is oxidized to a related 2-electron cluster, [Cp*3W3O6]+, which was crystallized and characterized in three different salts, 2-4. The 3-electron cluster exhibits a near-tetragonal frozen-glass EPR spectrum, and it shows evidence of coupling of the unpaired electron to only one of the three W atoms. The two-electron cluster is diamagnetic. An electrospray ionization MS n study revealed a stepwise expulsion of neutral [Cp*WO 2] units as the main fragmentation process. DFT calculations unveiled the intimate details of the electronic structures of these complexes and fully rationalized the structural and spectroscopic properties. © Wiley-VCH Verlag GmbH & Co. KGaA, 2007.Item Rational, facile synthesis and characterization of the neutral mixed-metal organometallic oxides Cp*2MoxW6-xO 17 (Cp* = C5Me5, x = 0, 2, 4, 6)(Wiley-VCH Verlag, 2009) Taban-Çahskan G.; Agustin D.; Demirhan F.; Vendier L.; Poli R.The reaction of the bis(pentamethylcyclopentadienyl)pentaoxidodimetal complexes Cp*2M2O5 with four equivalents of Na2M′O4 (M, M′ = Mo, W) in acidic aqueous medium constitutes a soft and selective entry into neutral Lindqvist-type organometallic mixed-metal oxides Cp*2MoxW 6-xO17 [x = 6 (1), 4 (2), 2 (3), 0 (4)]. The identity of the complexes is demonstrated by elemental analyses, thermogravimetric analyses and infrared spectroscopy. Thermal degradation of 1-4 up to above 500 °C leads to Mox/6W1-;x/6O3. The molecular identity and geometry of compound 2 is further confirmed by a fit of the powder X-ray diffraction pattern with a model obtained from, previously reported, single-crystal X-ray structures of 1 and 4, with which 2 is isomorphous. DFT calculations on models obtained by replacing Cp* with Cp (I-IV) validate the structural assignments and assist in the assignment of the M,M′-O vibrations. © Wiley-VCH Verlag GmbH & Co. KGaA.Item Molybdenum versus tungsten for the epoxidation of cyclooctene catalyzed by [Cp*2M2O5](Wiley-VCH Verlag, 2013) Sözen-Aktaş P.; Manoury E.; Demirhan F.; Poli R.The catalytic activity of [Cp*2M2O5] (M = Mo, W; Cp* = pentamethylcyclopentadienyl) for the homogeneous epoxidation of a solution of cyclooctene in MeCN/toluene follows the order Mo >> W when using tert-butyl hydroperoxide (TBHP)/decane as oxidant, in contrast to the inverse order (W >> Mo) when using aqueous H 2O2 as oxidant. The catalytic activity for the Mo system strongly depends on the solvent used to deliver the oxidant (TBHP/decane >> TBHP/H2O). The low activity of the W system is also decreased when using TBHP/water in place of TBHP/decane. For both metals, H 2O2/H2O is a better oxidant than TBHP/H 2O. However, whereas the Mo-based catalyst is much more active for the TBHP/decane epoxidation in spite of the lower TBHP oxidizing power (TBHP/decane > H2O2/H2O > TBHP/H 2O), the W-based system is much more active for the H 2O2/H2O epoxidation in spite of the negative effect of water (H2O2/H2O > TBHP/decane > TBHP/H2O). The kinetic profile of the TBHP/decane epoxidation process is affected by product inhibition. Initial rate measurements show that the rate law is first order with respect to substrate and has saturation behavior with respect to the oxidant. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Item Surface nanocrystallization of SAE 1008 steel by single and multipass thread rolling process; [Nanokristallisierung der Oberfläche von SAE 1008 Stahl durch Ein- und Mehrfach-Gewindewalzen](Wiley-VCH Verlag, 2017) Kahraman F.; Gençer G.M.; Kahraman A.D.In this study, the layers are investigated which are obtained on the surfaces of the single and multi-pass thread rolled screws. It is observed that deformation is more homogenous depending on the pass number and thread laps failure do not form on the 3-passed threads. A nanocrystallized layer that thicknesses and size depends on deformation amount is determined on the surfaces of the thread rolled SAE 1008 steel. While top of this layer has finer grain sizes, depending on the deformation amount grains coursed and oriented by the deformation direction. The finer grains are observed in the single pass thread rolled sample as size of 136 nm at the 15 μm inside from the surface of the root of the thread. Compared with bulk material, significant hardness increase is observed on the surfaces of the all thread rolled samples. The effect of pass number on the hardness is very low, increases of the pass number, hardness increases slightly. But thicknesses of layer are enhanced to increase the pass number. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimItem Design, synthesis, and in vitro biological evaluation of novel thiazolopyrimidine derivatives as antileishmanial compounds(Wiley-VCH Verlag, 2020) Istanbullu H.; Bayraktar G.; Akbaba H.; Cavus I.; Coban G.; Debelec Butuner B.; Kilimcioglu A.A.; Ozbilgin A.; Alptuzun V.; Erciyas E.A series of thiazolopyrimidine derivatives was designed and synthesized as a Leishmania major pteridine reductase 1 (LmPTR1) enzyme inhibitor. Their LmPTR1 inhibitor activities were evaluated using the enzyme produced by Escherichia coli in a recombinant way. The antileishmanial activity of the selected compounds was tested in vitro against Leishmania sp. Additionally, the compounds were evaluated for cytotoxic activity against the murine macrophage cell line RAW 264.7. According to the results, four compounds displayed not only a potent in vitro antileishmanial activity against promastigote forms but also low cytotoxicity. Among them, compound L16 exhibited an antileishmanial activity for both the promastigote and amastigote forms of L. tropica, with IC50 values of 7.5 and 2.69 µM, respectively. In addition, molecular docking studies and molecular dynamics simulations were also carried out in this study. In light of these findings, the compounds provide a new potential scaffold for antileishmanial drug discovery. © 2020 Deutsche Pharmazeutische GesellschaftItem Optimization of weld bead geometry of laser welded ANSI 304 austenitic stainless steel using grey-based Taguchi method; [Optimierung der Schweißraupengeometrie von laserstrahlgeschweißtem austenitischem ANSI 304-Edelstahl unter Verwendung der grau-basierten Taguchi-Methode](Wiley-VCH Verlag, 2020) Gencalp Irizalp S.; Koroglu B.K.This paper investigates the quality characteristics of the welding geometry of the laser welding process for the ANSI 304 austenitic stainless steel, with the use of a pulsed Nd:YAG laser welding system. Laser welding of 2 mm thick ANSI 304 stainless steel is performed at three different levels of three factors, i. e., peak power, welding speed and pulse duration. In this study, a multi-response optimization problem is developed to achieve weld bead geometry with full penetration as well as a narrow bead width and minimum crater. Grey relational analysis based on Taguchi orthogonal array is used to present an effective approach for the optimization of laser welding process parameters. Regression equations between the welding parameters and the bead dimensions for laser welded austenitic stainless steels are developed, which are used in predicting the penetration, width and crater. Finally, the equations are tested for values different from the levels of the parameters in the orthogonal array. It will be beneficial to engineers for continuous improvement in laser welded product quality. © 2020 Wiley-VCH GmbHItem Characterization of hot forged P285NH steel by metallurgical investigation and reliability analysis; [Charakterisierung von warmgeschmiedetem P285NH-Stahl durch metallurgische Untersuchungen und Zuverlässigkeitsanalyse](Wiley-VCH Verlag, 2020) Saklakoğlu N.; Çivi C.; Hocalar Ç.; Demirok S.An extensive study was carried out to investigate the effect of cooling rate after hot forging process and normalization step on the hardness, strength and impact toughness and microstructure of P285NH steel. Understanding of the combined effect of cooling rate and normalization on the mechanical and microstructural properties of the steel would help to select conditions required to achieve optimum mechanical properties. The results indicated that the microstructures of all forging and cooling conditions were dominated by ferrite and pearlite phases with different morphologies and grain sizes according to various cooling rates. Conveyor cooling led to a formation of relatively fine acicular ferrite and pearlite grains in comparison to batch cooling which presented coarse polygonal ferrite with pearlite. Based on the data fluctuation of Charpy tests, the normal distribution provided a statistical analysis method for assessing the reliability. Through the statistical analysis of the distribution function, it can be concluded that normalization step is necessary for higher reliability. Both batch cooling and conveyor cooling did not give the required reliability level for safety components due to heterogeneities in the microstructure. © 2020 Wiley-VCH GmbHItem Enhanced Electrochemical Determination of Catechol and Hydroquinone Based on Pd Nanoparticles/Poly(Taurine) Modified Glassy Carbon Electrode(Wiley-VCH Verlag, 2020) Koçak Ç.C.; Koçak S.Here, Pd nanoparticles and poly(taurine) film was prepared on the glassy carbon electrode surface (Pd/Poly(TAU)/GCE) by the rapid electrochemical technique. The proposed composite surface was characterized by scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS) and electrochemical impedance spectroscopy(EIS). Enhanced electron transfer ability and higher electroactive surface area were achieved at Pd/Poly(TAU)/GCE as compared to the bare GCE and polymer film electrode. The new and highly stable Pd/Poly(TAU)/GCE was employed for the individual and simultaneous determination of hydroquinone and catechol which were environmentally toxic. Under the optimized conditions, HQ and CC were individually determined by using the differantial pulse voltammetry in the linear ranges of 0.008–100 μM and 0.001–100 μM with the detection limits of (LOD) 2.1 nM and 0.68 nM, respectively. In case of simultaneous determination, LODs were found as 10 nM and 0.88 nM for HQ and CC, respectively. The content of both analytes in the real sample analysis was evaluated in the river water and tap water successfully. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimItem Pulsed Deposited Manganese and Vanadium Oxide Film Modified with Carbon Nanotube and Gold Nanoparticle: Chitosan and Ionic Liquid-based Biosensor(Wiley-VCH Verlag, 2020) Akoğulları S.; Çιnar S.; Özdokur K.V.; Aydemir T.; Ertaş F.N.; Koçak S.Present study describes the synthesis of mixed oxide films of manganese and vanadium by electrochemical pulsed deposition technique on a glassy carbon electrode (GCE) modified with multiwall carbon nanotubes (MWCNT). The film was further decorated with gold nanoparticles to enhance the reduction signal of dissolved oxygen in pH 5.17 acetate buffer solution. All of the electrochemical synthesized modified electrodes have been characterized with Scanning electron microscopy(SEM), High-resolution transmission electron microscopy (HRTEM), X-Ray photoelectron spectroscopy (XPS), X-Ray diffraction (XRD) techniques. The electrode obtained (AuNPs/MnOx−VOx/CNT/GCE) was utilized as a platform for glucose biosensor where the glucose oxidase enzyme was immobilized on the composite film with the aid of chitosan and an ionic liquid. The electrochemical performance of the biosensor was investigated by cyclic voltammetry and the relative parameters have been optimized by amperometric measurements in pH 5.17 acetate buffer solution. The developed biosensor exhibited a linear range for glucose between 0.1–1.0 mM and the limit of detection was calculated as 0.02 mM. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, WeinheimItem Platinum Nanoparticles/Poly(isoleucine) Modified Glassy Carbon Electrode for the Simultaneous Determination of Hydroquinone and Catechol(Wiley-VCH Verlag, 2021) Koçak S.A new electrochemical sensor based on Poly(Isoleucine) modified glassy carbon electrode decorated with platinum nanoparticles (Pt/Poly(Isoleucine)/GCE) was developed for sensitive individual and simultaneous determination of hydroquinone (HQ) and catechol (CC). Scanning electron microscopy (SEM), Electrochemical impedance spectroscopy (EIS), Cyclic voltammetry (CV) and Differential pulse voltammetry (DPV) were performed in order to characterize the Pt/Poly(Isoleucine)/GCE nanocomposite. For simultaneous determination of HQ and CC, Pt/Poly(Isoleucine)/GCE showed wide linear range between the 0.01–100.0 μM. The detection limits were 0.006 μM for HQ and 0.005 μM for CC. The Pt/Poly(Isoleucine)/GC electrode exhibited good sensitivity and reliability in the simultaneous electroanalysis of two isomers in PBS of pH 7.5. The modified electrode was used to detect the isomers in naturel samples. © 2020 Wiley-VCH GmbH